a. Field of the Invention
The present invention generally relates to microprocessors, and more particularly to maintaining the performance of such microprocessors using control circuitry.
b. Background of Invention
Microprocessor devices should operate reliably across a variety of environmental conditions. One occurrence associated with microprocessor environments is voltage droop, whereby as a result of, for example, changes in current load, the supply voltage momentarily drops. Voltage droop may in turn affect the maximum operating frequency (fmax) of the microprocessor compared to the actual frequency at which the microprocessor is being driven. For example, the microprocessor may be operating at a nominal clock frequency of 4.5 GHz, while the maximum operating frequency (fmax) of the microprocessor may be characterized as being 4.7 GHz. Thus, a guardband of 200 MHz (i.e., 4.7 GHz−4.5 GHz=0.2 MHz) exists.
According to one scenario, a voltage drop may cause the maximum operating frequency (fmax) of the microprocessor to reduce to 4.6 GHz while the microprocessor continues to operate at the nominal clock frequency of 4.5 GHz. Here, the microprocessor continues to operate within the provided guardband since the nominal frequency (i.e., 4.5 GHz) remains below the fmax(i.e., 4.6 GHz) of the microprocessor. However, according to another scenario, the voltage drop may be significant enough to cause the maximum operating frequency (fmax) of the microprocessor to reduce to, for example, 4.3 GHz while the microprocessor continues to operate at the 4.5 GHz nominal frequency. Here, the microprocessor fails to operate within the provided guardband since the nominal frequency (i.e., 4.5 GHz) is now higher than the fmax (i.e., 4.3 GHz) of the microprocessor. Therefore, as a result of driving the microprocessor at a nominal frequency (i.e., 4.5 GHz) that is beyond the momentarily reduced fmax (i.e., 4.3 GHz) value, the microprocessor operation may fail.